1. Field of the Invention
This invention relates to the conversion of blood types of B erythrocytes into type O cells to render for use in transfusion therapy. More especially, this invention relates to a process for the conversion of B erythrocytes into type O cells under conditions whereby the cells do not lose their cellular functions, are suitable for the adsorption and release of oxygen whereby the cells can be transfused in the manner of type O blood. This invention also relates to the products obtained by the conversion of such B erythrocytes into type O cells.
2. Discussion of Prior Art
As is well known in transfusion therapy, it is necessary to match the blood type of the recipient with the type of blood available in the blood bank. Thus, for instance, a recipient of type A blood can only be safely transfused with type A blood. The exception to this is type O blood, the erythrocytes of which can be safely transfused into type A, type B and type A,B recipients as well as O recipients.
In the operation of a blood bank or other facility which accumulates whole blood or at least the red cell component thereof it is necessary to maintain supplies of each type of blood. It has not heretofore been possible to maintain only O type blood because there is a paucity of O type donors. O type donor blood has therefore been used largely for O type recipients. On the other hand, a majority of donors have A, B or AB blood and there can exist from time to time, an excess of these types of blood. It has become desirable, therefore, to adjust the supply to the demand. Specifically, it has been desired to convert A, B or AB type blood to an O type blood type--a universal donor.
The ABO blood group system was the first to be discovered and is the one of greatest importance from the point of view of blood transfusion. Individuals of blood types A,B and O express A,B and H antigens respectively. These antigens are not only found on the red cells but on the surfaces of all endothelial and most epithelial cells as well. In addition, glycoproteins having A,B and H antigenicity are also found in the tissue fluids and secretions of those individuals who have the ability, inherited as a Mendelian dominant character, to secrete these blood group substances, or factors as they are termed.
While the blood group substances are glycoproteins, the A B H active material obtained from cell membranes appear to be only glycolipids. For a time it was thought that blood group active glycoproteins, as well as glycolipids were present on the surface of the red cells. However, recent studies have shown that the A B H blood group activity so far found associated with glycoproteins isolated from the cell membrane is an artifact resulting from the isolation procedure.
Considerable work has been done to determine the structures of the A B H determinants. It was found that the blood group specificity of the entire molecule, which may contain one or more carbohydrate chains, attached to a peptide backbone, is determined by the nature and linkage of those monosaccharides situated at the non-reducing ends of these chains. The most important sugar for each specificity, often referred to as the immuno-dominant or immuno-determinant sugar, was found to be as follows: for H antigen, fructose; for a antigen, N-acetyl-galactosamine; and for the type B antigen, galactose. More recently, studies with A B H active glycolipids obtained from erythrocyte cell membranes also show the presence of the same immuno-dominant sugars at the reducing ends of the carbohydrate chains, attached to adjacent sugars by the same linkages. The carbohydrate chains, are, in turn, linked to the ceramide, which is imbedded in the lipid bi-layer of the membrane. The length of the carbohydrate moiety may vary and it may have either a straight or branched structure. Thus, far four variants of blood group active A glycolipid, two of B and three of H, have been isolated from the erythrocyte cell membrane.
Through these studies, it was theorized that one could convert a type A or type B antigen into a type H antigen, corresponding to a type O cell by removal of one of the monosaccharide groups pendent from the cell. Specifically, in the case of the B antigen, it was postulated that the galactose moiety of the type B antigen could be removed enzymatically whereby the type B antigen would be converted to a type H antigen. Flowers and collaborators (Harpaz, N., Flowers H. M. and Sharon, N. Arch. Biochem. Biophys. 170 676 (1975)) postulated that the terminal galactose moiety could be hydrolyzed away from B antigenic determinant of stroma obtained from B-type cells. See also Yatziv, S., and Flowers, H. M., Biochem. Biophys. Res. Commun. 45 514 (1971). Efforts for the removal of the terminal galactose moiety from the B-antigenic determinate of stroma and intact red cells were successful. However, where attempts were made to reproduce the procedures of the published literature it was observed that while the terminal galactose moiety was removed, that considerable hemolysis occurred with the red cells breaking down so that the resultant composition was not useful in transfusion therapy.
It is an object of this invention, therefore, to provide a process in which the terminal galactose moiety of the B-antigenic determinant of stroma from A and AB type cells can be removed while leaving the red cells intact so that the resultant composition can be used in transfusion therapy. Specifically, it is an object of this invention to convert B type cells to O type cells whereby the cells remain intact and undergo little if any hemolysis and the resultant composition can be employed in transfusion therapy.